1. Field of the Invention
The present invention relates to an endoscopic diathermic knife for performing endoscopic sphincterotomy (EST) or endoscopic papillotomy (EPT).
2. Description of the Related Art
Japanese laid-open patent publications 5-7597 and 5-68685 each disclose a diathermic knife, in which a knife portion is formed by exposing an electrically conductive wire introduced into a lumen of a tube to the outside of an external wall surface of a distal end portion of the tube. The distal end portion of the tube is bent in a bow-like shape by pulling the conductive wire by an operation on its proximal end side, and the knife portion is pushed on a part to be treated to cut it by a high frequency current. Such a diathermic knife employs a relatively soft tube so that the distal end portion of the tube can be easily bent.
Furthermore, Japanese examined patent publication 6-53125 discloses an instrument which is provided with a reinforcing means of a rectangular cross section in the range from the distal end portion to the proximal end portion within a lumen of a tube in order to control the direction of cutting a sphincter.
In the diathermic knives disclosed in Japanese laid-open patent publications 5-7597 and 5-68685, when the conductive wire is pulled by the operation on the proximal end side to bend the distal end portion of the tube in the bow-like shape, the tube is somewhat easy to bend because it is soft. However, since the tube flexes over its full length, there has been the operational problem that the distal end portion of the tube can not be easily bent due to frictional resistance between the conductive wire and the lumen of the tube.
Further, there has been the problem that, when such a diathermic knife is pushed into a treating instrument inserting channel of an endoscope and a narrow cavity in a living body, the tube also flexes in its axial direction and the pushing operation on the proximal end side is not effectively transmitted to the distal end portion so that its insertion is not easy.
When the endoscopic sphincterotomy is performed by using such an endoscopic diathermic knife, the knife is used usually with an endoscope of a side view type having a bending mechanism and a treating instrument upheaving device.
First, the endoscope is inserted into a duodenum and bent by a bending operation thereof to observe a duodenal papilla directly. Next, the endoscopic diathermic knife is introduced through a treating instrument inserting channel of the endoscope and inserted into a bile duct through the papilla by the operation of the treating instrument upheaving device and the bending operation. Then, the conductive wire is pulled by the operation on the proximal end side of the endoscopic diathermic knife to bend the distal end portion of the tube in a bow-like shape, and the knife portion is pushed on a duodenal papillary sphincter to cut it by a high frequency current.
FIG. 6 shows how the endoscopic sphincterotomy is performed, and FIG. 8 shows an endoscopic image of the state shown in FIG. 6
As shown in FIG. 6, in order to observe the papilla directly, it is necessary from an anatomical point of view to bend the bending portion of the endoscope so that the center of curvature is on the side of the field of view of the endoscope. Moreover, in order to bring the endoscopic diathermic knife to the field of view of the endoscope and easily insert the distal end into the bile duct, it is necessary to upheave the endoscopic diathermic knife toward the field of view of the endoscope by operating the treating instrument upheaving device.
Furthermore, as shown in FIG. 8, in order to perform the endoscopic sphincterotomy safely without causing complications, it is necessary to cut upward in the plane of the paper, that is, the so-called twelve o'clock direction within the field of view of the endoscope.
Accordingly, as shown in FIG. 6, when performing the endoscopic sphincterotomy, the bending direction of the endoscope, the direction of upheaving the endoscopic diathermic instrument by the treating instrument upheaving device, and the knife portion in the distal end portion of the tube are positioned substantially in the same plane, and the distal end portion of the tube has a bending shape with the knife portion directed inwardly.
In imitation of the aforesaid bending shape of the tube, doctors give a bending tendency to the distal end portion of the tube beforehand so as to direct the knife portion inward, so that the knife portion is directed to the twelve o'clock direction in the field of view of the endoscope when the endoscopic diathermic knife goes out of the distal end portion of the endoscope. That is, the bending tendency of the tube is fitted to the bending shape of the endoscope and the direction of the treating instrument upheaving device to stabilize the direction of the knife portion.
However, the doctors cannot always give the bending tendency stably to the distal end portion of the tube. Accordingly, there has been the problem that the direction of the knife portion with respect to the endoscope is not stable.
If the reinforcing means provided in the lumen of the tube of the instrument as disclosed in Japanese examined patent publication 6-53125 is applied to the endoscopic diathermic knives as disclosed in Japanese laid-open patent publications 5-7597 and 5-68685, the problems of operation and insertion caused by the flexing of the entire tube of the aforesaid endoscopic diathermic knife will be somewhat solved because the full length of the tube is reinforced.
Moreover, by virtue of the regulation of the bending direction of the tube by the reinforcing member of the instrument in Japanese examined patent publication 6-53125, the bending direction of the tube coincides with the bending shape of the endoscope and the direction of the treating instrument upheaving device, so that the problem of the direction of the knife portion will be solved.
However, in the instrument of Japanese examined patent publication 6-53125, because the reinforcing member is provided also in the lumen of the knife portion in the distal end portion of the tube, the reinforcing member becomes resistant to the bending when the distal end portion of the tube is bent in a bow-like shape. Consequently, the problem of not being able to easily handle the distal end portion of the tube is not solved.
Moreover, because the distal end portion of the tube is rigid, when inserting the distal end portion of the tube into the bile duct through the papilla, a part near the papilla and the inside wall of the bile duct will be injured, and danger of causing other complications such as perforation and bleeding is high, thereby raising a problem of safety.